Ok, your suggestion worked (if it is right, and it appears to be):

```
ebin_sizes = get_bin_sizes(ebins)
czbin_sizes = 2.0*np.pi*get_bin_sizes(czbins)
bin_sizes = np.meshgrid(czbin_sizes,ebin_sizes)
aeff_hist /= np.abs(bin_sizes[0]*bin_sizes[1])
```
I'm trying to figure out why on earth that is correct though...